WEDNESDAY, Feb. 28, 2018 (HealthDay News) -- It's a myth that people with heart disease who are overweight or obese live longer than those who are normal weight, researchers report.

Rather than living longer than normal-weight people, those who are obese are just diagnosed at a younger age, the study found. They spend more of their lives with heart disease, but actually live shorter lives.

The study, from Northwestern University researchers, refutes the so-called "obesity paradox."

"The obesity paradox caused a lot of confusion and potential damage because we know there are cardiovascular and non-cardiovascular risks associated with obesity," said researcher Dr. Sadiya Khan. She's an assistant professor of medicine (cardiology) and preventive medicine at Northwestern.

"I get a lot of patients who ask, 'Why do I need to lose weight if research says I'm going to live longer?' " Khan said in a university news release. "I tell them losing weight doesn't just reduce the risk of developing heart disease, but other diseases like cancer."

"Our data show you will live longer and healthier at a normal weight," she said.

For their study, the researchers compared the risk for stroke, heart attack, heart failure and cardiovascular disease among men and women who were 40 to 50 years old and of varying weights.

They found that the risk for the various cardiovascular conditions was 21 percent higher in overweight men and 67 percent higher in obese men, compared with normal-weight men.

Among women, the risk was 32 percent higher in those who were overweight and 85 percent higher in those who were obese, compared with women of normal weight.

As for longevity, men who were obese lived 1.9 years less than normal-weight men. The study found little difference in length of life between overweight and normal-weight men.

Among women, however, those who were overweight lived 1.4 years less, and those who were obese lived 3.4 years less than normal-weight women.

The study was published Feb. 28 in the journal JAMA Cardiology.

"A healthy weight promotes healthy longevity or longer 'healthspan' in addition to lifespan, so that greater years lived are also healthier years lived," Khan said. "It's about having a much better quality of life."